Determinants of bone mineral density in stable kidney transplant recipients

Kidney transplant recipients (KTR) are at increased risk for bone loss. Determinants of bone mineral density (BMD) in an unselected KTR population have not previously been described.

We conducted a cross-sectional analysis of 389 stable KTRs undergoing bone mineral densitometry assessment by dual-energy X-ray absorptiometry at the lumbar spine, total hip and femoral neck. Risk factors for osteopenia and osteoporosis were determined by t-tests or ANOVA and chi-square analysis as appropriate. Factors associated with reduced BMD were ascertained using multivariate linear regression.

At the lumbar spine, 247 demonstrated normal BMD, 115 had osteopenia and 27 osteoporosis. Corresponding prevalence rates for the total hip and femoral neck were 222/143/24 and 178/184/27, respectively. Osteopenia or osteoporosis was more prevalent at the femoral neck than lumbar spine (p=0.002). Osteopenia or osteoporosis at the spine, hip and femoral neck were highly correlated (p<0.0001). Independent associations with reduced BMD included female sex (p<0.0001) and lower body mass index (p<0.0001) at all sites, age for total hip and femoral neck (p=0.0001), and hyperparathyroidism (p=0.036), time posttransplant (p=0.0001) for the femoral neck, with no association by renal function or 25-OH vitamin D level at any site.

Significant bone loss in KTRs is most prevalent at the femoral neck. Identifying risk factors for specific sites may allow for earlier intervention prior to osteoporosis development.